Electrically insulated electroluminescent display

ABSTRACT

An electroluminescent display has a transparent front-electrode, rear electrodes, and a layer of electroluminescent material located between the first and second electrodes. Conductive tracks are electrically connected to the rear electrodes and supply a driving voltage for the electroluminescent material to the rear electrodes. A backplane layer is provided between the electroluminescent material layer and the conductive tracks, and is electrically connected to the front electrode such that the potential difference across the electroluminescent material layer in the region of the conductive tracks is substantially zero. In this way, when the conductive track is supplying the driving voltage to the rear-electrodes, the electroluminescent material layer is not illuminated by an electric field between the conductive tracks and the front electrode. Gaps may be defined in the front electrode corresponding substantially to the location of the conductive tracks. This also prevents the voltage in the conductive tracks from illuminating the electroluminescent material layer. An addressable electroluminescent display may be included in an item of clothing.

BACKGROUND OF THE INVENTION

The present invention relates to electroluminescent displays.

Electroluminescence is the emission of light by a material whensubjected to an electric field. Phosphor electroluminescence wasdiscovered and documented in 1936. However, it was only in the 1950'sthat GEC and Sylvania received patents for electroluminescent powderlamps. The short lifetime, for example 500 hours, of such deviceslimited their usefulness.

Work carried out in the 1980's revitalised the powder electroluminescentlamp, and in 1990 the Durel Corporation demonstrated a flexibleelectroluminescent phosphor device that was incorporated as a backlightinto a liquid crystal flat panel display. The manufacturing techniqueinvolved encapsulating the phosphor powder particles in glass beads andsandwiching the encapsulated powder between two electrodes, to which anAC voltage was applied to stimulate emission. Electroluminescent devicesmade according to this type of method are known as “thick film” or“powder” electroluminescent devices. This is to be contrasted with “thinfilm” electroluminescent devices, in the manufacture of which a thinlayer of electroluminescent phosphor is deposited on a, typically glass,substrate by a method such as atomic layer epitaxy.

Traditionally, thin film technology has been used to makeelectroluminescent displays, and thick film technology has been used tomake electroluminescent lamps, in particular backlights for liquidcrystal displays (LCDs). An example of a thin film device is describedin U.S. Pat. No. 5,463,279, and an example of a thick film device isdescribed in U.S. Pat. No. 5,686,792.

A typical thick film phosphor electroluminescent device comprises alayer of electroluminescent material in a dielectric matrix, sandwichedbetween two planar conducting electrodes. The electroluminescentmaterial comprises phosphor particles, typically a zinc sulphide (ZnS)powder doped with manganese (Mn), microencapsulated in a dielectricmaterial. Typically, silver- or graphite-loaded screen-printable inks,and indium tin oxide (ITO), a transparent conductive material,respectively are used to form the electrodes on a substrate such as apolyester film. When an AC voltage is applied between the electrodes,the electroluminescent material emits light.

The inventors have recently developed thick film electroluminescentdisplays in which a plurality of shaped independent electrodes areprovided on at least one side of a layer of shaped or unshapedelectroluminescent material. A voltage may be applied selectively toeach of these independent electrodes to illuminate a respective regionof the display. A thick film electroluminescent display is created byselecting the configuration of the independent electrodes to representinformation, for example in the form of a seven-segment display or thelike.

Thus, the inventors have recently developed an addressableelectroluminescent display, i.e. an electroluminescent displaycomprising a plurality of display areas each having the shape of agraphical element wherein each display area may be separately,selectively illuminated.

A problem associated with the manufacture of thick filmelectroluminescent displays is that the independent electrodes must beconnected electrically to a voltage source for the display. In aconvenient manufacturing technique, electrical connections are appliedas conductive tracks on the rear surface of the device, for example byscreen printing conductive ink. However, the tracks themselves can actas electrodes and cause the electroluminescent phosphor to emit lightwhere the phosphor is sandwiched between a transparent front electrodeand the conductive track. Thus, the conductive tracks appear asilluminated lines on the display and adversely affect the clarity of thedisplayed information, which is undesirable.

U.S. Pat. No. 5,686,792 relates to an electroluminescent lamp with acontinuous electroluminescent dielectric layer and a patterned rearelectrode overlying the electroluminescent dielectric layer. The rearelectrode includes at least two conductive segments separated by a gap.An insulating layer fills the gap and a conductive interconnect overliesthe insulating layer, joining the segments. The insulating layer spacesthe interconnect from the electroluminescent dielectric layer asufficient distance to reduce the electric field in theelectroluminescent dielectric layer below the point at which the lampappears luminous.

The solution to the problem of visible electrical interconnections inthe context of an electroluminescent lamp provided by U.S. Pat. No.5,686,792 has certain disadvantages. For example, the depth of theinsulating layer is fixed by the manufacturing process and this depthdetermines a maximum voltage which can be applied to the rear electrodewithout causing illumination of the electrical connections in theelectroluminescent display. Furthermore, the thickness of the insulatinglayer must be carefully controlled to ensure the invisibility of theinterconnections, and this places additional constraints on themanufacturing process. Also the thickness and inflexibility of theinsulating layer adds to the overall thickness of the display anddetracts from its flexibility.

SUMMARY OF THE INVENTION

The present invention seeks to provide a novel configuration of anelectroluminescent display in which the electrical connections to theelectrodes of the display are not visible as illuminated regions of theelectroluminescent material.

Viewed from a first aspect therefore the invention provides anaddressable electroluminescent display comprising:

-   -   a first layer comprising an electrically-conductive,        transparent, front-electrode;        -   a second layer comprising a plurality of            electrically-conductive, rear-electrode segments;        -   a third layer located between the first and second layers            and comprising electroluminescent material;        -   a fourth layer comprising a plurality of            electrically-conductive tracks each of which is electrically            connected at a first end to at least one of the            rear-electrode segments;        -   a fifth layer located between the fourth layer and a sixth            layer (defined below), comprising dielectric material and            following substantially the path of the            electrically-conductive tracks; and        -   a sixth layer located between the third and the fifth            layers, comprising an electrically-conductive, backplane            which:        -   is electrically connected to the front-electrode in front of            the backplane such that the potential difference across the            third layer in the region of the sixth layer is            substantially zero;        -   follows substantially the path of the            electrically-conducting tracks;            wherein, in use, a driving voltage for driving the            illumination of an area of the display is supplied across            the first layer and a rear electrode segment in the second            layer.

Thus according to the invention, in the region of theelectrically-conductive tracks (or “electrical conductor”), theelectrically conductive backplane (or “sixth layer” or “electricallyconductive layer”) ensures that there is substantially no potentialdifference across the electroluminescent material layer (or “thirdlayer”), even if the electrically-conductive tracks are supplyingdriving voltage, and the electrically-conductive tracks therefore do notcause the electroluminescent material to illuminate.

The first layer (or “first, transparent electrode”) may comprise a layerof a transparent conductive material, for example indium tin oxide,applied to a transparent substrate, for example a polyester film. Thetransparent conductive material may be applied to the transparentsubstrate by any suitable method, for example screen printing,sputtering and the like.

The configuration of the display is such that information can berepresented by the display by the application of a voltage to selectedrear-electrode segments (or “second electrodes”). For example the areasthat can illuminate (“display areas”) may be arranged in a numeric oralphanumeric display arrangement, such as a seven, fourteen or sixteensegment display.

The rear-electrode segments may be provided on the display by anysuitable method, such as by screen printing with conductive, for examplesilver- or graphite-loaded, inks.

The electroluminescent material in the third layer (or “layer ofelectroluminescent material”) is a thick film phosphor layer, forexample zinc sulphide powder doped with manganese and microencapsulatedin a dielectric material.

The electrically-conductive tracks may be formed on the device by anysuitable method, such as by screen printing with conductive, for examplesilver- or graphite-loaded, inks. Feasibly, some electrically-conductivetracks may be formed on the device together with the rear-electrodesegments. In this case, these electrically-conductive tracks may beconsidered as an extension of the relevant rear-electrode segments. Atleast part of the electrically-conductive tracks may be integral withthe rear-electrode segments.

In general, a respective electrically-conductive track is provided foreach rear-electrode segment.

The sixth layer (or “electrically conductive layer”) may be arranged insubstantially the same plane as the second layer. Thus, for example, therear-electrode segments may be provided in one or more voids or recessesdefined in the sixth layer. In this case, the spacing between the sixthlayer and the rear-electrode segments, defined by the size of the voids,should be selected to prevent arcing due to potential differencesbetween the sixth layer and the second layer.

A layer of dielectric material (or “fifth layer” or “first dielectriclayer”) is provided to insulate electrically the electrically-conductivetracks from the sixth layer, as there may be a significant potentialdifference between these components. Thus, such a dielectric layer musthave sufficient electrical insulation capability to withstand thedriving voltage for the electroluminescent material. This dielectriclayer may be applied by any suitable method, such as screen printing.

In a preferred arrangement, the sixth layer is provided over the secondlayer. This arrangement has the advantage that the registration of thesixth layer relative to the second layer does not need to be as accurateto ensure correct electrical functioning of the device as when therear-electrode segments are provided in voids or recesses in the sixthlayer.

A further dielectric layer (or “second dielectric layer”) may beprovided to electrically insulate the second layer from the sixth layer,which will generally be at different potentials in use of the device.Such a dielectric layer may be applied by any suitable method, forexample screen printing.

It is advantageous for any voids which exist in the sixth layer and anydielectric layers (for the purpose of allowing theelectrically-conductive tracks to connect to the rear-electrodesegments) to be made as large as possible in order to minimise theeffect of any mis-registration of the sixth layer (and/or the associateddielectric layer(s)), the rear-electrode segments and theelectrically-conductive tracks.

The sixth layer follows substantially the path of theelectrically-conductive tracks, in order to reduce the cost of materialsand to reduce registration problems associated with other methods. It isdesirable for the fifth layer to cover a greater area than the sixthlayer, so that electrical insulation is generally assured even in thecase of variations in the registration of these layers. Likewise, it isdesirable for the sixth layer to cover a greater area than theelectrically-conductive tracks, so that the electrically-conductivetracks are generally not visibly illuminated even in the case ofvariations in the registration of the sixth layer relative to theelectrically-conductive tracks.

Preferably, the sixth layer and the associated dielectric layer(s)overlap the area of the rear-electrode segments in order to allow fortolerances in the registration of the sixth layer and the associateddielectric layer(s) relative to the electrically-conductive tracks.

Preferably, the overall area of the sixth layer and the associateddielectric layer(s) is maintained as small as possible to minimise theprobability of a short circuit due to imperfections, such as pin holes,in the dielectric layer(s).

The sixth layer may comprise a plurality of separate portions, eachelectrically connected to the relevant part of the first layer. In otherwords, the backplane may comprise a plurality of electrically conductivebackplane track elements 7 as shown in FIG. 3. Each of the backplanetrack elements 7 is associated with one or more of theelectrically-conductive tracks 9, has substantially the sametwo-dimensional form as, but is wider than, its associatedelectrically-conductive track and stops short of its associatedelectrically conductive track 9. FIG. 3 also illustrates anelectroluminescent display in which the fifth layer comprises aplurality of dielectric tracks each of which is associated with one ofthe electrically-conductive tracks and each of which dielectric trackshas substantially the same two-dimensional form as, but is wider thanits associated electrically-conductive track and, at a first end, stopsshort of the first end of its associated electrically-conductive track.

FIG. 3 illustrates an addressable electroluminescent display in whichbackplane track-elements 7 are provided substantially exclusively inareas of the display in which there exists electroluminescent materialand a front electrode and an electrically-conductive track 9. FIG. 3further illustrates an addressable electroluminescent display in whichthe backplane track-elements 7 are provided substantially exclusivelyoutside of display areas at which the second layer is shaped in the formof the graphical element.

FIG. 4 illustrates a further embodiment of an electroluminescent displayincluding a plurality of electrically conductive, transparent frontelectrodes 1 a, 2 a, 1 b, 2 b. In the embodiment of FIG. 4, theelectroluminescent material is also configured as a plurality ofseparate electroluminescent material segments 3 a, 3 b.

A void (or gap) may be provided in the first layer opposite anelectrically-conductive track, so that an electric field is notgenerated between the first layer and the electrically-conductive track,which would cause the electroluminescent material to illuminate in theregion of the electrically-conductive track. The void(s) may be definedin the first layer by etching or otherwise ablating (e.g. using lasers)the transparent conductive material from the transparent substrate.Alternatively, the transparent conductive material may be applied to atransparent substrate in a configuration which defines the void(s).

According to the invention, electroluminescent devices may be made whichare flexible, lightweight and relatively inexpensive. Advantageously, anelectroluminescent display may be incorporated into an item of clothing.

Thus, viewed from a second aspect the invention provides an item ofclothing comprising an addressable electroluminescent display with aplurality of display areas each having the shape of a graphical elementand each of which may be separately, selectively illuminated.

The electroluminescent display may be arranged to display informationrelating to the wearer of the clothing. For example, the display mayrepresent an amount of oxygen which remains in the tanks of breathingapparatus used by a fire-fighter or a diver. Similarly, the displaycould represent the elapsed time from the start of a race for aparticular athlete.

The electroluminescent display may include additional electronics forcontrolling the display. For example, the display may includeshort-range communication electronics for example utilising the DECT orBlue Tooth communications protocols.

Advantageously, the electroluminescent display may comprise anelectroluminescent device according to the first aspect of theinvention.

Although the invention has been described in terms of the structure ofan electroluminescent display, the invention also extends to a method ofmaking such a display as described herein.

Viewed from a yet further aspect, the invention provides anelectroluminescent display comprising:

-   -   a first, transparent electrode;    -   at least one second electrode;    -   a layer of electroluminescent material located between the first        and second electrodes;    -   an electrical conductor in the form of a conductive track,        electrically connected to the second electrode and arranged to        supply, in use, a driving voltage for the electroluminescent        material to the second electrode;    -   an electrically conductive layer which is provided between the        electroluminescent material layer and the electrical conductor,        substantially following the path of the electrical conductor,        said conductive layer being electrically connected to the first        electrode, such that the potential difference across the        electroluminescent material layer in the region of the        electrical conductor is substantially zero; and    -   a first dielectric layer located between the electrical        conductor and the conductive layer.

BRIEF DESCRIPTION OF THE DRAWINGS

Some embodiments of the invention will now be described by way ofexample only, and with reference to the accompanying drawings, in which:

FIG. 1 is a schematic representation of an electroluminescent displayshowing some aspects of the invention;

FIG. 2 is an exploded view of the device of FIG. 1;

FIG. 3 is a schematic representation of an electroluminescent displayshowing aspects of the invention; and

FIG. 4 is an exploded view of an alternative embodiment of anelectroluminescent display illustrating aspects of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

As shown in FIG. 1 an electroluminescent display according to theinvention comprises a substrate layer 1 of transparent polyester, whichis prefabricated with a layer of indium tin oxide (ITO) 2 to form atransparent front-electrode. A layer of thick film electroluminescentphosphor material 3 is provided on top of the ITO layer 2. A firstdielectric layer 4 is provided over the phosphor layer 3, and on top ofthe first dielectric layer 4 is provided a rear-electrode 5 ofscreen-printed silver-loaded ink. The rear-electrode 5 is covered by asecond dielectric layer 6. The second dielectric layer 6 electricallyisolates the rear-electrode 5 from a backplane layer 7, also ofscreen-printed silver-loaded ink. On top of the backplane layer 7 isprovided a third dielectric layer 8, which electrically isolates thebackplane layer 7 from an electrically-conductive track 9.

The electrically-conductive track 9 thus runs in a longitudinaldirection between a point at one end of the track where it is connectedto a rear-electrode segment and a point at another end of the trackwhere it is connected either directly or indirectly to a voltage supply.The direction of “width” (as used herein) of the electrically-conductivetrack and of other tracks associated with the electrically-conductivetrack is defined as that direction which is substantially perpendicularto the longitudinal direction of the electrically-conductive track.

As shown in FIG. 1, the backplane layer 7 is electrically connected tothe ITO layer 2 so that these two layers are always at the sameelectrical potential.

In use, an AC driving voltage of 100 to 600 volts is applied between arear-electrode segment 5 (via the conductive track 9) and the ITO layer2, in order to generate an electric field across the electroluminescentphosphor 3 so that the phosphor emits light.

The conductive backplane layer 7 is always at substantially the sameelectrical potential as the ITO layer 2, and is located between thephosphor layer 3 and the conductive track 9. There is therefore noelectric field across the electroluminescent phosphor layer 3 due to thedriving voltage in the conductive track 9. In effect, the backplanelayer 7 shields the electroluminescent phosphor layer 3 from the drivingvoltage in the conductive track 9, so that the phosphor layer 3 is notilluminated by the conductive track 9.

Although the third dielectric layer 8, the backplane layer 7, and thesecond dielectric layer 6, are represented in FIG. 2 as having voidsdefined therein for the conductive track 9, for a display according tothe invention, the third dielectric layer 8, the backplane layer 7, andthe second dielectric layer 6, in fact, follow substantially the path ofthe conductive track 9, in order to reduce the cost of materials and toprevent registration problems between these layers, as shown in FIG. 3.

FIG. 3 shows a plurality of rear electrodes 5 which are configured toform the hour, minute and second hands on the top part of an analogueclock display. Electrically-conductive tracks 9 are connected to theserear electrodes 5. The conductive tracks 9 sit on a second dielectriclayer (not shown in FIG. 3) which in turn sits on a backplane layer 7which in turn sits on a first dielectric layer 4.

In summary, an electroluminescent display comprises a transparentfront-electrode 1,2, a rear-electrode 5, and a layer ofelectroluminescent material 3 located between the front and rearelectrodes. A conductive track 9 is electrically connected to therear-electrode 5 and supplies a driving voltage for theelectroluminescent material 3 to the second electrode 5. A backplanelayer 7 is provided between the electroluminescent material layer 3 andthe conductive track 9, and is electrically connected to the frontelectrode 1,2, such that the potential difference across theelectroluminescent material layer 3 in the region of the conductivetrack 9 is substantially zero. In this way, when the conductive track 9is supplying the driving voltage to the rear electrode 5, theelectroluminescent material layer 3 is not illuminated by an electricfield between the conductive track 9 and the front electrode 1,2.

Note that although the description has mainly described embodiments inwhich the shape of illuminated areas are defined by the rear electrodes,this shape may alternatively be defined by appropriate shaping of thefront electrode or the electroluminescent material layer or acombination of the front electrode, the electroluminescent material andthe rear electrode.

It is also to be noted that, with suitable provision of driving voltages(that is, actively driving “on” displays areas to be illuminated and“off” display areas to not be illuminated), there is no need for abackplane layer to be provided in areas behind rear-electrode segments,since those rear-electrode segments which are driven “off ” (i.e. set tothe same voltage as the transparent, front-electrode) act in the sameway that such a backplane layer would and ensure thatelectrically-conductive tracks which run behind them cannot cause anyillumination of the electroluminescent material in front of them. It isfurther to be noted that there is also no need to provide a backplanelayer in areas of the display where there is either no front-electrodeor no electroluminescent material or no electrically-conductive track.

In an alternative arrangement (not shown), a gap is defined in the frontelectrode 1,2 corresponding substantially to the location of theconductive track 9. This also prevents the voltage in the conductivetrack 9 from illuminating the electroluminescent material layer 3.

An electroluminescent display may be included in an item of clothing.

It is possible to prevent the unwanted illumination of the electricalconductors without the use of a conductive layer as described above.

In this case, an electroluminescent device comprises:

-   -   a first, transparent electrode;    -   at least one second electrode;    -   a layer of electroluminescent material located between the first        and second electrodes; and    -   an electrical conductor electrically connected to the second        electrode and arranged to supply, in use, a driving voltage for        the electroluminescent material to the second electrode,    -   wherein a void is defined in the first electrode corresponding        substantially to the location of the electrical conductor.

Thus a void (or gap) is provided in the first electrode opposite theelectrical conductor, so that an electric field is not generated betweenthe first electrode and the electrical conductor, which would cause theelectroluminescent material to illuminate in the region of theelectrical conductor.

1. An addressable electroluminescent display comprising: a first layercomprising an electrically-conductive, transparent, front-electrode; asecond layer comprising a plurality of electrically-conductive,rear-electrode segments; a third layer located between the first andsecond layers and comprising electroluminescent material; a fourth layercomprising an plurality of electrically-conductive tracks each of whichis electrically connected at a first end to at least one of therear-electrode segments; a fifth layer located between the fourth layerand a sixth layer (defined below), comprising dielectric material andfollowing substantially the path of the electrically-conductive tracks;and a sixth layer located between the third and the fifth layers,comprising an electrically conductive backplane which: is electricallyconnected to the front-electrode in front of the backplane such that thepotential difference across the third layer in the region of the sixthlayer is substantially zero; and follows substantially the path of theelectrically-conductive tracks; wherein, in use, a driving voltage fordriving the illumination of an area of the display is supplied acrossthe first layer and a rear electrode segment in the second layer.
 2. Anaddressable electroluminescent display according to claim 1, comprisinga plurality of display areas each having the shape of a graphicalelement and each of which may be separately, selectively illuminated,wherein, at each display area, at least one of the first, second orthird layers is shaped in the form of the graphical element.
 3. Anaddressable electroluminescent display according to claim 2, wherein thebackplane of the sixth layer comprises a plurality ofelectrically-conductive, backplane track-elements.
 4. An addressableelectroluminescent display according to claim 3, wherein each of thebackplane track-elements: is associated with one of theelectrically-conductive tracks; has substantially the sametwo-dimensional form as, but is wider than, its associatedelectrically-conductive track; and stops short of the first end of itsassociated electrically-conductive track.
 5. An addressableelectroluminescent display according to claim 4, wherein the fifth layercomprises a plurality of dielectric tracks each of which is associatedwith one of the electrically-conductive tracks and each of whichdielectric tracks has substantially the same two-dimensional form as,but is wider than its associated electrically-conductive track and, at afirst end, stops short of the first end of its associatedelectrically-conductive track and wherein the backplane of the sixthlayer comprises a plurality of electrically-conductive, backplanetrack-elements, wherein each of the backplane track-elements stops shortof the first end of the associated dielectric track.
 6. An addressableelectroluminescent display according to claim 3, wherein backplanetrack-elements are provided substantially exclusively in areas of thedisplay in which there exists electroluminescent material and a frontelectrode and an electrically-conductive track.
 7. An addressableelectroluminescent display according to claim 3, wherein backplanetrack-elements are provided substantially exclusively outside of displayareas at which the second layer is shaped in the form of the graphicalelement.
 8. An addressable electroluminescent display according to claim1, wherein the first layer comprises a plurality of separateelectrically-conductive, transparent, front-electrode segments.
 9. Anaddressable electroluminescent display according to claim 1, wherein thethird layer comprises a plurality of electroluminescent materialsegments.
 10. An addressable electroluminescent display according toclaim 1, wherein the fifth layer comprises a plurality of dielectrictracks each of which is associated with one of theelectrically-conductive tracks and each of which dielectric tracks hassubstantially the same two-dimensional form as, but is wider than itsassociated electrically-conductive track and, at a first end, stopsshort of the first end of its associated electrically-conductive track.11. An addressable electroluminescent display according to claim 1,further comprising a dielectric layer located between the second layerand the third layer.
 12. An addressable electroluminescent displayaccording to claim 11, wherein the dielectric layer substantiallyfollows the path of the electrically-conductive tracks.
 13. Anaddressable electroluminescent display according to claim 1, wherein atleast one of the second layer, the fourth layer and the sixth layer isformed as a conductive track on a printed circuit board.
 14. Anaddressable electroluminescent display according to claim 1, wherein thesecond layer, the fourth layer, the fifth layer and the sixth layer areformed as the layers of a multi-layer printed circuit board.
 15. Anelectroluminescent display comprising; a first, transparent electrode;at least one second electrode; a layer of electroluminescent materiallocated between the first and second electrodes; an electrical conductorin the form of a conductive track, electrically connected to the secondelectrode and arranged to supply, in use, a driving voltage for theelectroluminescent material to the second electrode; an electricallyconductive layer which is provided between the electroluminescentmaterial layer and the electrical conductor, substantially following thepath of the electrical conductor, said conductive layer beingelectrically connected to the first electrode, such that the potentialdifference across the electroluminescent material layer in the region ofthe electrical conductor is substantially zero; and a first dielectriclayer located between the electrical conductor and the conductive layer.16. A device as claimed in claim 15, further comprising a seconddielectric layer located between the second electrode and the conductivelayer, wherein the conductive layer and the first and second dielectriclayers overlap the area of the second electrode.
 17. A device as claimedin claim 15, wherein at least one of the second electrode, theconductive layer and the electrical conductor is formed as a conductivetrack on a printed circuit board.
 18. An item of clothing comprising anelectroluminescent display, wherein the electroluminescent displaycomprises an electroluminescent device as claimed in claim
 15. 19. Anitem of clothing comprising an addressable electroluminescent displaywith a plurality of display areas each having the shape of a graphicalelement and each of which may be separately, selectively illuminated,wherein the addressable electroluminescent display comprises: a firstlayer comprising an electrically-conductive, transparent,front-electrode; a second layer comprising a plurality ofelectrically-conductive, rear-electrode segments; a third layer locatedbetween the first and second layers and comprising electroluminescentmaterial; a fourth layer comprising a plurality ofelectrically-conductive tracks each of which is electrically connectedat a first end to at least one of the rear-electrode segments; a fifthlayer located between the fourth layer and a sixth layer, comprisingdielectric material and following substantially the path of theelectrically-conductive tracks; and a sixth layer located between thethird and the fifth layers, comprising an electrically-conductive,backplane which is electrically connected to the front-electrode infront of the backplane such that the potential difference across thethird layer in the region of the sixth layer is substantially zero andfollows substantially the path of the electrically-conductive tracks;wherein, in use, a driving voltage for driving the illumination of anarea of the display is supplied across the first layer and a rearelectrode segment in the second layer.